Treatment of motor fuel



Patented Aug. 29, 1933 PATENT OFFICE TREATMENT OF MOTOR FUEL Charles D; Lowry, Jr.,

and Charles G. Dryer,

Chicago, 111., assignors to Universal Oil Products Company, Chicago, 111., a corporation of South Dakota No Drawing. Application October 5, 1931 Serial No. 567,136

3 Claims.

This invention relates to the treatment of motor fuels and refers more particularly to the treatment of low boiling gasoline mixtures produced from the cracking of heavy hydrocarbon 5 oils, though similar boiling range gasolines produced from crude oils by non-cracking distillation methods can also be treated.

More specifically, the invention has reference to processes of treatment whereby the deterioration of such fuels on storage under varying influence of light, air, etc, is substantially prevented and the invention is also concerned with the particular characteristics of the products resulting from these treatments.

The rapid increase in the use of the automobile engine in the last two or three decades has necessitated increasing its supply of suitable fuel. For a time the natural gasoline content of. the petroleum produced supplemented to some extent by light coal tar products and gasoline recovered from natural gas suificed to meet the needs of the trade. However, as the production and use of the internal combustion engine began to increase disproportionately to the supply of fuel the problem of providing an adequate supply was attached from two general standpoints, first, to increase the efficiency of the engines by increasing the compression ration and, second, by increasing the amount of low boiling motor fuel fractions obtained from the various crude oils. Fortunately these two developments were not antagonistic since the additional yields of gasoline produced by cracking the heavier portions of the crude petroleums after the natural gasoline had been removed were found to possess slow burning characteristics rendering them highly suitable for use in high compression engines. These slow burning or anti-knocking characteristics were found to be due to the presence of relatively large percentages 40 of hydrocarbons having a cyclic structure similar to benzol and to a lesser extent to unsaturated compounds of a straight chain or olefinic structure.

Prior to the advent of the cracking process as a factor in the trade, the straight run gasolines produced either by simple distillation from crudes or by absorption from casing head gases were of an essentially saturated character, containing only negligible amounts of olefinic and cyclic hydrocarbons so that they underwent substantially no change when stored for long periods of time, particularly if reasonably protected from the influence of light and air.

The cyclic compounds contained in cracked gasolines are essentially of a stable character resistant to oxidizing or polymerizing influences.- However, the more unsaturated olefinic constituents such as the di and tri olefins are characterized by a tendency to deposit gummy or resinous materials upon standing particularly under the influence of light and air and are objectionable for this gum-forming tendency and also on account of their loss as possible anti-knock material. During the gum-forming period in the storage of a cracked gasoline, a yellow to brownish color develops which is distinctly undesirable from a sales standpoint. Therefore, it has been necessary in most cases to subject cracked gasolines to treatments for the removal of highly unsaturated hydrocarbons and sulphur compounds to render them suitable for marketing.

Experiments conducted Within comparatively recent years have demonstrated that it is possible to stabilize the anti-knock value, the color and the gum content of cracked gasolines by the use of very minor amounts of certain organic and inorganic chemical compounds which act to inhibit the polymerization tendencies of the more highly unsaturated olefins and which are generally antioxygenic in character.

The field of choice for the selection of particular compounds for inhibiting deterioration of cracked gasoline may be limited to those compounds Which will inhibit separately or collectively the formation of gum, color or anti-knock value, although in most instances the formation of gums is accompanied by a loss in anti-knock value, either on account of loss of unsaturated compounds per se or on account of the knocking characteristics of the polymers formed or for other reasons.

Inhibitors are to be distinguished from antiknock agents in that the true anti-knock agent modifies the combustion of fuel in an internal combustion engine cylinder but does not necessarily prevent the development of undesirable characteristics under storage. In fact, numerous well-defined anti-knock agents are themselves unstable in storage and the gasoline to which they are added needs further additions of true inhibitors to stabilize the increased anti-knock value produced by the addition of the anti-knock agent. Furthermore, it is usually necessary to use much higher percentages of reagents to prevent knocking than is necessary in inhibiting deterioration and depreciation of the gasoline so that it will be seen that in the great majority of cases the action of anti-knock agents is distinct from that of true inhibitors, the use of which constitutes the present invention.

In one specific embodiment the invention comprises the use of aldol alpha naphthylamine to inhibit the deterioration of the valuable quanities of gasoline on storage.

The compound mentioned has been found to have special value which sharply differentiates it from compounds previously used for the same purpose. Being a condensation product of aldol and alpha naphthylamine it appears to exhibit the inhibiting properties of both in a degree which is more than additive, and to possess also the properties of ease of handling, ready availability and proper solubility. The various aldols that are known are not usually sufliciently soluble in gasoline to permit their use as inhibitors of gum and color formation in cracked gasoline. Also while alpha naphthylamine has inhibiting value, this property is definitely enhanced by the substitution of the aldol residue for the hydrogen atoms in the amino group. At the present time there is not enough known about the relation between the structural formula: of inhibitors and their inhibiting value to make predictions as to the possible value of the compound on the basis of its chemical composition. The discovery of the outstanding value of the compound used according to the present invention proves this point as there was not enough definite evidence at hand to foresee its value.

As far as theories have been evolved to account for the rather startling effect of the addition of very low percents of inhibitors to unsaturated hydrocarbon mixtures, it would appear that they act as anti-oxidants or negative catalyzers for the initial oxidizing reactions which result eventually in the formation of gums by induced polymerization of highly unsaturated olefinic compounds. Since the type of compound which can act as an inhibitor is invariably one which is easily oxidized, the theory has been evolved that the initial oxidizing reactions form peroxides of both the unsaturated hydrocarbons and the inhibitor, which initially formed peroxides are antagonistic and result in their mutual decomposition in a manner similar to the mutually destructive action of potassium permanganate and hydrogen peroxide. Thus the extensive oxidation of the oil is prevented and the compounds stabilized which otherwise would form undesirable gummy and colored compounds.

The use of a compound as an inhibitor is of course, limited by its solubility in the fuel to be stabilized but in many instances this is not a deciding factor on account of the extremely small amounts which it is necessary to use, sometimes as low as 0.01%. In the case of extremely insoluble compounds, they may be dissolved in the proper solvent and added in solution to the fuel. The solubility factor may be more pronounced when the inhibiting substances are to be added to oils heavier than gasoline such as, for example, I

kerosene transformer oils, and lubricating oils.

As examples of results obtained when utilizing the compounds of the present invention in stabilized cracked gasolines against the effects of light and air, the results obtained when testing such gasolines (with and without the addition of inhibitors) in the recently developed oxygen bomb may be cited. This method of testing allows the approximate determination in a relatively short time of the effect of long time storage upon the gasoline. Briefly, the bomb test consists in heating a small sample of the gasoline in an oxygen atmosphere at pressures above atmos-' pheric under controlled conditions so that the time in which the absorption of oxygen becomes noticeably accelerated is determinable. The time elapsing from the beginning of the heating up to the point where relatively rapid oxygen absorp tion begins has been designated as the induction period of the sample under test and the possession of an induction period of 3 to 4'hours has been tentatively adopted to indicate a gasoline'blend which can be stored under refinery and sales station conditions without anticipation. of the development of undesirable color and gums and deterioration in anti-knock value.

The compound whose use is proposed in the present invention when used in amounts of 0.1% or less in numerous cracked gasolines has invariably raised the induction period in the oxygen bomb test to a time above 4 hours, whereas alpha naphthylamine used similarly raised the induction period to only approximately 1 hours, on an average. From this, it will be evident that the introduction of the aldol residue as heretofore described has produced a novel condensation product which is of value in stabilizing gasolines against the deteriorating influences of light, air and storage.

We claim as our invention:

1. A method for preventing the deterioration of cracked gasoline containing di-olefins'and'trioleflns in respect to gum or color formation and knock rating, which comprises admixing therewith a small amount of aldol alpha naphthylamine.

2. A method for preventing the deterioration of cracked gasoline containing di-olefins and triolefins in respect to gum or color formation and knock rating, which comprises admixing therewith aldol alpha naphthylamine in quantities not exceeding one-tenth of one percent.

3. Motor fuel comprising cracked gasoline containing a small amount of aldol alpha naphthylamine as a stabilizer for the highly unsaturated oleflnic content of the gasoline.

. CHARLES D. LOWRY, JR.

CHARLES G. DRYER. 

